resistance of leather to acid

The maximum percentage of acid that a leather is
capable of absorbing without deteriorating with
time. Experiments involving both chrome- and
vegetable-tanned calfskins indicate that rapid
destruction of the chrome-tanned leather may be
expected if the percentage (by weight of leather)
of (sulfuric) acid exceeds 10%, while a percentage
greater than 4% of the same acid will cause rapid
deterioration of the vegetable-tanned skin. Most
of the acid found in the chrome-tanned skin is
probably in chemical combination with the
chromium, whereas in the vegetable-tanned skin it
exists as free acid. (363 )